THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -Fertilization and completion of meiosis. (A) Fertilization induces the transition from metaphase II to anaphase II, leading to completion of oocyte meiosis and emission of a second polar body (which usually degenerates).

Detailed explanation-2: -Following fertilization, the egg exits from meiosis and assembles a haploid pronucleus. At the same time the sperm genome, which enters the egg in a highly compact state, undergoes decompaction. Sperm protamines are replaced by histones and the male haploid pronucleus is formed.

Detailed explanation-3: -Meiosis only occurs in reproductive cells, as the goal is to create haploid gametes that will be used in fertilization. Meiosis is important to, but not the same as, sexual reproduction. Meiosis is necessary for sexual reproduction to occur, as it results in the formation of gametes (sperm and eggs).

Detailed explanation-4: -Explanation: The secondary oocyte completes meiosis II only when fertilized by a spermatozoan. After fertilization is initiated, the secondary oocyte begins its second meiotic division, resulting in the formation of a mature ovum and another polar body. At this point, the ovum is ready to fuse with the spermatozoan.